Which of the following is NOT a type of musical interval?

The classification of musical intervals includes types such as perfect, diminished, major, and others. The term "harmonic" typically refers to a way intervals can be played or perceived, rather than a distinct type of interval itself.

Musical intervals are defined based on the number of half steps between the notes. A perfect interval could refer to perfect fourths and fifths. Diminished intervals are a half step smaller than perfect or major intervals, making them important in scale and chord structures. Major intervals are larger than minor intervals and signify a specific relationship between notes.

In contrast, "harmonic" describes an aspect of music concerning how intervals sound together when played simultaneously rather than indicating a specific categorization of intervals themselves. Hence, it does not fit within the standard naming conventions of intervals as the others do.